In the 3rd Generation Partnership Project (3GPP) protocol, a Long Term Evolution (LTE) system includes an access network and a System Architecture Evolution (SAE) core network.
FIG. 1 is a schematic architectural diagram of an SAE core network in a control domain. An external network element 01, for example, an eNodeB (evolved NodeB), an AF (application function) entity, or a GW-U (Gateway User-plane), may interact with each controller 03 in the control domain by using a network element selector (NES) 02. Each controller 03 is connected to a database server 04. The database server 04 may be configured to store resource information such as subscription data and context data of all UEs (user equipment) in a current control domain. After receiving a user request initiated by UE and forwarded by the network element selector 02, the controller 03 may interact with the database server 04 to implement functions such as mobility management, session management, and charging and policy management. The network element selector 02 may select, based on a load status of each controller 03 and a preconfigured load balancing policy, a controller 03 having relatively low load to process the user request, to balance load of all controllers 03 in the current control domain and implement optimized utilization of resources in the current control domain.
However, when the load of all the controllers 03 is greater than a load threshold, the current control domain is overloaded. In this case, when any UE initiates a new user request, the network element selector 02 needs to wait for an idle controller 03 and then can allocate the controller 03 to the user request. This increases a communication delay between the UE and the SAE core network.